Using a laser and a tiny section of reflective material on the leaf of the plant, researchers were able to measure the movement of the leaf in response to the chewing caterpillar.
According to a report from the University of Missouri-Columbia (MU), building on previous studies that suggested plant growth can be influenced by sound and that plants respond to wind and touch, researchers used a collaboration of audio and chemical analysis to determine that plants respond to the sounds that caterpillars make when eating plants and that the plants respond with additional defenses.
“Previous research has investigated how plants respond to acoustic energy, including music,” said Heidi Appel, senior research scientist in the Division of Plant Sciences in the College of Agriculture, Food and Natural Resources and the Bond Life Sciences Center at MU. “However, our work is the first example of how plants respond to an ecologically relevant vibration. We found that feeding vibrations signal changes in the plant cells’ metabolism, creating more defensive chemicals that can repel attacks from caterpillars.”
Appel worked with Rex Cocroft, professor in the Division of Biological Sciences at MU. Over the course of the study, the researchers placed caterpillars on Arabidopsis, a small flowering plant related to cabbage and mustard. Using a laser and a tiny section of reflective material on the leaf of the plant, Cocroft was able to measure the movement of the leaf in response to the chewing caterpillar.
Following this experiment, Cocroft and Appel played back recordings of caterpillar feeding vibrations to one set of plants, but played back only silence to the other set of plants. When caterpillars afterward fed on both sets of plants, the researchers found that the plants previously exposed to feeding vibrations produced more mustard oils, a chemical that is unappetizing to many caterpillars.
Appel and Cocroft say future research will center on how vibrations are sensed by the plants, what features of the complex vibrational signal are key, and how the mechanical vibrations interact with other forms of plant information to produce protective responses to pests.
The researchers also produced a video report that shows how the sounds of caterpillars eating the leaves of Arabidopsis plants influences the production of additional defenses, which can be found here.
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